1. Field
Aspects of the present invention relate to ion exchange membrane filling compositions, methods of manufacturing ion exchange membranes, ion exchange membranes, and redox flow batteries, and more particularly, to ion exchange membrane filling compositions including ion conductive materials and water soluble supports, methods of preparing ion exchange membranes by using the ion exchange membrane filling compositions, ion exchange membranes prepared by using the methods, and redox flow batteries including the ion exchange membranes.
2. Description of the Related Art
A typical secondary battery converts electric energy input thereto by changing the electric energy into chemical energy and then stores the chemical energy. Then, during discharging, the battery converts the stored chemical energy into electric energy and then outputs the electric energy.
Like the typical secondary battery, a redox flow battery also converts electric energy input thereto by changing the electric energy into chemical energy and then stores the chemical energy. Then, during discharging, the redox flow battery converts the stored chemical energy into electric energy and outputs the electric energy. However, the redox flow battery is different from the typical secondary battery in that because an electrode active material retaining energy is present in a liquid state, not in a solid state, a tank for storing the electrode active material is needed.
In detail, in a redox flow battery, a catholyte and an anolyte each function as an electrode active material, and a typical example of these electrolytes is a transition metal oxide solution. That is, in a redox flow battery, the catholyte and the anolyte are stored in a tank in the form of a solution including a redox transition metal in which the oxidation state is changed.
Also, in a redox flow battery, a cell for generating electric energy has a structure of cathode/ion exchange membrane/anode, and the catholyte and anolyte supplied to the cell via a pump contact corresponding electrodes, respectively. At the respective contact surfaces, transition metal ions included in the respective electrolytes are oxidized or reduced. At this point, an electromotive force corresponding to the Gibbs free energy is generated. In this case, the electrodes do not directly participate in the reactions and only aid oxidation/reduction of transition metal ions included in the catholyte and the anolyte.
In a redox flow battery, the ion exchange membrane does not participate in the reactions and performs (i) a function of quickly transferring ions that constitute a charge carrier between the catholyte and the anolyte, (ii) a function of preventing direct contact between a cathode and an anode, and most importantly (iii) a function of suppressing crossover of electrolyte active ions that are dissolved in the catholyte and the anolyte and directly participate in the reactions.
However, a conventional ion exchange membrane for a redox flow battery is mainly used to selectively separate ions in an aqueous system, and accordingly, ion mobility characteristics and film properties in the aqueous solution are optimized. However, an ion exchange membrane for a redox flow battery that has optimized ion mobility characteristics and film properties in a non-aqueous system, that is, an organic system, has not yet been sufficiently studied.